diff --git a/models/HabitList.py b/models/HabitList.py
index 110af65..e20ac25 100644
--- a/models/HabitList.py
+++ b/models/HabitList.py
@@ -62,7 +62,10 @@ class HabitList:
     # Adds a User by email to the HabitList
     def add_user(self, email: str):
         user = User.get_by_email(email)
-        add_user(self.id, user.id)
+        if user:
+            add_user(self.id, user.id)
+        else:
+            return None
 
 
     # Removes a User from the HabitList